Means for and method of regulating the transmission over electric circuits



A. B. CLARK. MEANS FOR AND METHOD OF REGULATING THE TRANSMISSION OVER ELECTRIC CIRCUITS APPLICATION FILED SEPT. I0, I918.

Patented Dec. 12, 1922 A TTORNEY Federated cc. 12, W22.

stares ALVAJB. CLARK, OF BROOKLYN, HEW YGBK, ASSXGNOR T0 AMERICAN TELEPHONE AND TELEGRAPH COMIANY, A CORPORATION OF'NEW YORK.

MEANS F03, AND METHOD (3F REG-HEATING TEE TRANSMISSION OVER ELECTRIC GIBC'UITS.

Application filed ficptemher 10, 1918. Serial Ito. 253,485.

To all whom it inay concern:

Be it known that l, ALVA B. Cryre siding at Brooklyn, in the county of Kings and State'oi New York, have invented certain Improvements in Means for and Methods of Regulating the Transmission Over Electric Circuits, of which the following is a specification,

This invention relates to transmission circuits, and more particularly to transmission circuits of the type known as fourwire circuits, altho h it is in general applicable to transmission circuits of anykind. The principal object of the invention is to provide suitable methods and means for maintaining substantially constant the transmission equivalent of a circuit regardless of variations in the conditions afiecting the electrical characteristics of the ciredit. Other and further objects will, however, be clear from the description of the invention hereinafter given. I

In general, the transmission equivalent eta circuit varies, due to a number of different causes. If the transmission circuit be of the four-wire type, in which a pair of separate transmission lines are employed for transmitting in opposite directions, these causes may be divided into two classes: The first class comprises causes which affect both sides of the circuit, or in other words, both transmission lines, in the same manner. Among these causes may be enumerated variations in the resistance of the conductors, loading .coils, etc., variations in capacity, inductance, or other electrical characteristics of the-cable, and variations in the potential of repeater batteries common to repeaters in both sides of the circuit. The second class comp-rises causes which afiect the two sides difi'e-rently, such as variations in the structure of repeater bulbs where vacuum tube repeaters are employed; variations in the potentials of grid batteries, or accidental variations due to the resistance of bad joints, leakage due to poor insulations, etc. i

In therase of transmission circuits in which only one transmission line is used for transmission in the two directions, the factor of variation with respect to the two sides of the circuit will generally be absent but some or all of the above causes may contribute to produce variations in the transmission equivalent of the circuit, thereby rendering it highly desirable that some provision be made for overcoming the effect of these variations.

The present invention contemplates eliminating these diificulties by varying some adjustable element of the transmission circuit to compensate for the variations introduced into the circuit. In general a. number of methods may be employed in carrying out the objects of this invention. For example,

the effects due to some one cause, such as.

temperature variations, may be compensated for by observing the changes produced in one circuit of a cable and then varying in accordance with such changes, similar elements of a number of circuits which are affected in a like manner. In the case of a four-w1re circuit, whereit 1s dGSlIGdtllO take into account variatlons which do not affectboth sides of the circuit alike, adjustment may be made for each side of the,

ations in the circuit, or at intervals of suitable frequency. For purposes of illustration, apparatus is disclosed for automatical- The objects of the invention are secured as herein disclosed by disconnecting the ends of the two transmission lines, comprising a four-wire circuit, from their termi hating arrangements, and interconnecting the ends through adjustable-transmission devices capable of introducing transmission losses or gains which together are adjusted to have a transmission equivalent double and opposite in sign to, that to .which the sides of the four-wire circuit exclusive of the terminals are to beadjusted. The path thus formed will sing when the amplification therein exceeds the loss,.and the cir-,. N cuit' will have the proper transmission 90 y ly carrying out the last method above mentioned, but it will be understood that man- -ual apparatus may be employed if desired.

equivaleni; when it is edjnslzed to e critical point at which singing just begins or just ceases. Accordino'ly by arbiirarily bringing the amplifice'eion of the path Well below the singing point end fallen grsduolly adjusiing the circuit independently of said interconnec zing nn'iii singingjust begins or by raising iiie emplificniion Well above the initial singing point and ually adjusting the circuit until singing just ceases fihe cirini will be set for the proper iransmission equivalent.

Where the letter method is employed the smpliiicsiion in ills closed path may be incressed unlil it is greater than the toisl loss, preferably by increasing the amplificaiion oi? chews repeaters in the ewe trans mission lines of the four-wire circuit. This causes singing'lo place around dais closed path and by gradually decreasing the amplification of similar amplifiers in the two transmission lines until singing just ceases, which occurs when the toiel amplification is spproxirnetely equal to the total I loss, lillfi four-vvire circuit will be set for the desired transmission equivalen In order "to perform *ehese functions automatically the circuit may be so arranged that when the iJWO ends of the four-Wire circuit are interconnected, an automatic svviich controlling the setting of the goiaentiometers which determine the empli caiion of the repeaters, will be resiored to a normal condition. in which the poteniiometers are set to permit the greoitesc ossible amplification. Singing then flakes 1p ace and an alternating current relay responsive to the singing oscillations may be arranged to control the advancing of the switch until the potentiometers are at e position such that singing just ceases.

The invention may now be more fully understood from the following description .when read in connection with the accompanyin drawing, Figure l of which is a schema'eic diagram of an arrengerneni in which the invention may be embodied while Fig. 2 is o circnitdiagram showing on automatic apparatus for carrying out the invention as applied to s. four-Wire circuit.

Referring to Fig. 1, s four-Wire circuit is shown interconnecting two terminal stetions C and D, said four-wire circuit comprising a pair of transmission lines L and L for transmittingin opposite directions. it will be understood that these transmission lines may include one way repeaters (not shown) for securing desired transmission over the cir. nit. At the terminal station the founwire circuit may be assoelated by means of the usual three-Winding brensformers 1 and 2., with terminating two- Wire. lines L end L said two-wire lines being balanced by suitable artificial lines N and N When it is desired to adjust the transmission of the four-wire circuit as L and may be disconnected fro: h ir terminal. arrangements by means of relays 3, i, 5 end -83 only she coniscis of which are in llig. 1. By means o these relays the ends of the lines L and may be iniyerconne through the adj nsi slole t ssion devices ill Z and M indicoied These devices may i should so detransmission equiv lo and epposiii'e n. C50, is it is desired. y'she sides of ilie iowswire sin cuitexclusive of the i-erinin l zrppsrd 1*. shell be odjused. in other wolf" the ends of e 1 Move is ioesi is dou-- um, desired to arrange the :ioi'ir-Wire that each of its two sides will sire e oer toin gein in transmission -Qhe devices 3' and M should together e mission loss equel to twice the desired On the other hand, if ii. is desired there shall be a certain erensniission i each of the two sides the devices M end should comprise inn,plifiuers. or oiliermesns whereby a total tIilRSmlSSlOD gain eqoel twice the desired loss may be produced. order to simplify the srrengemeni, the devices l /i end M may be combined oi; one station so that at the other elation the ends of she transmission lines L and L, are directly connected. in order to ilie transmission equivalent of the fonrovire circuit, transmission varying devices X and X which will give either losses or may be provided in lines L and L respecto which tively. These devices should fiZSi) be sci pleite loop is zero, so that the actual trans mission equivalent of chat porbion of the loop comprising the lines L and L and the transmission varying devices X and X is equal to, but opposite in sign to. time of the devices M and M Assuming that she devices M and M have been properly the four-wire circuit will now have the do sired transmission equivalent. Turning now to Fig. 227

hi'cb shows in more detail an arrangement corresponding to that illustrated schematically in v i, ii will beseen time emplifiers A and i, are inserted in the lines L and L, respectively. and correspond to the devices X and X respectively of Fig. 1. in order to control the emplificsiii'on of these amplifiers, poi/entic meters P and P, are provided, the setting of said potentiometers being determined b an automatic switch, including wipers S ands Relays 3, 4, 5 and 6 are shown forthe purpose of disconnecting the transmis sion lines L and L from the terminating arrangement at stations C and D, and for interconnecting the ends of said lines in order to re late the transmission thereof. At station I the lines L and L, may be directly connected over path 7. At station D the ends of these lines are interconnected through an adjustable transmission device comprising an amplifier A corresponding to the device M, of Fig. 1. Bridged across the path including the amplifier A, is an alternating current relay V, which responds to singing over the four-wire circuit to control the stepping magnet 8, whereby the switch including wipers S and S is advanced. The relays 3, 4, 5 and 6, as well as relay 9, are included serially in a simplex circuit passing over the two sides of the line L,. Any other suitable circuit connecting the terminals of the four-wire circuit may, of course, be employed. This circuit is normally closed, but is opened by means of switches 10 and 11 when connections are completed over the two-wire lines L and L to the four-wire circuit, thereby deenergizing relay 9, and relays 3, 4, 5 and 6. Relays 3, 4:, 5 and 6 upon being deenergized, connee-t the tour-wire circuit to the terminal arrangement. The simplest circuit controlling these relays may also be opened by means of a switch 12 which may be either hand operated, or may be operated at regular intervals by means of a suitable timing arrangement. When the simplex circuit is again closed upon the taking down of the connection over lines L ahd L or by the closing of switch 12, the relays 3, 4:, 5 and 6 again disconnect the four-wire circuit from the terminal arrangement and interconnect the ends of the lines L, and L The relay 9 at the same time advances a commutator arrangement 13 one step so that the brush thereof passes over a live segment of the commutator and sends a momentary impulse through the release magnet 14 of the potentiometer cbntrolling switch to restore said switch. to tits normal position, in which position singing takes place over the four wire circuit, thereby actuating the alternating current relay V so that the switch is advanced step by step until singing just ceases.

Assuming that the amplifier A, has been properly adjusted as explained, upon completing a connection over linesL and L, the switches 10 and 11 will be opened, thereby breaking the normally closed circuit through relays 3, 4, 5, 6 and 9. his circuit may be traced from battery. over switch 10, switch 12, through the windings of relays (i and 3, thence in parallel over the two conductors of the transmission line L,, through the windings of relays 9, 5 and 4, and over switch 11 to ground. Relays 3, 4:, 5 and 6 release their armatures so that the ends of .wire circuit. The release-of magnet 9 permits its armature to retract and engage a new toot-h of the commutator arrangement 13, but no circuit change results therefrom. When the connection over lines L and L is taken down, switches 10 and 11 are again closed to complete the simplex circuit already traced through relays 3, 5 and 6, and through magnet 9. Relays 3, 4, 5 and 6 disconnect the transmission lines L and L from the terminal arrangements and interconnect the ends of said lines through the amplifier A The magnet 9 is energized at the same time, and in attracting its armature advances the commuator arrangement 13 one step, during which the brush of the commutator passes over alive segment thereof and again rests upon an insulating segment. A momentary impulse of curt'ent is thereby caused to flow through the release magnet 14, which withdraws the pawl carried by the armature of step magnet 8 *trom the ratchet Wheel of the switch S, S, per-- mitting the switch to be restored to its fnd mal condition, as indicated in the diagram; With the switch in this position, potentiometers P and P are so set that the greatest degree of amplification is produced by the through the winding of step magnet 8 to batter The switchS S, is now advanced .step by step until singing just ceases, when the relay V releases its armature and the switch remains in its advanced position, with the potentiometers P, and P, so set that the transmission equivalent of each of the lines L and L exclusive of their terminating arrangements, is opposite in sign to and equal to one half that of the amplifier A,. It, therefore, the amplifier A, has been properly set,'the four-wire clrcuit will have the desired transmission e uivalent.

The potentiometers P, and P, wi 1 remain.

in their set positions, and the circuit is now in condltion to be used.

The same result may be secured by opening and again closing the switch 12 either manually or by means of a time controlled device. It will also be obvious that the automatic switch arrangement may be eliminated, if desired, and the adjustment of the potentiometers may he performed manu ally.

By means of the arrangement disclosed, a four-wire circuit may be adjusted so that it Will have any desired transmission equiva lent, regardless of variations which may take place in the circuit, so long as the variations attect both sides of the circuit alike. It will also be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated, Without departing from the spirit of the invention as defined in the following claims.

What is claimed is:

1. In a four-wire circuit comprising a pair of transmission lines Tor transmitting in opposite directions and provided with means whereby said lines may be interconnected through terminal connections to terminal lines or connected together independently of said terminal connections, the method of adjusting the transmission efficiency of the four-wire circuit, which consists in producing a transmission path over a loop including the two lines of the tour-wire circuit interconnected independently of the terminal connections, and producing a condition. in the transmission path such that the amplitication is greater than the loss, so that singing takes place, and gradually adjusting the circuit until the amplification becomes slightly less than the loss, so that singing ceases.

2. In a four-wire circuit comprising a pair of transmission lines for transmitting in opposite directions and provided with means wher ,by said lines may he interconnected through terminal connections to terminal lines or connected together independently of said terminal connections, the method of adjusting the transmission efficiency of the four-wire circuit, which consists in producing a transmission path over a loop including the two lines of the fourwire circuit interconnected independently of the terminal connections, and adjusting the circuit until a condition is reached determined by Whether or not the circuit sings, under which the amplification in the loop is substantially equal to the loss.

3. In ai ourovire circuit comprising a pair of transmission lines for transmitting" in opposite directions and provided with means whereby said lines may be interconnected through tern'linal connections to terminal lines or connected together independently of said terminal connections, the method of adjusting the transmission eiiiciency of the four-wire circuit, which consists in producing a transmission path over a loop includ ing the two lines of the four-wire circuit interconnected independently ot the terminal connections, producing an ahnormal transmission condition in the -loop, and ad justing the transmission equivalent of the lines or interconnected independently of said terminal connections with a transmission de vice having total transmission equivalent opposite in sign and twice that to which it is desired to adjust the four-wire circuit, the method of adjusting the transmission efficiency of the four-wire circuit, which consists in producing a transmission path over a loop including the two lines of the tourwire circuit with their ends connected together through said transmission device independently ot the terminal connections, producing an abnormal transmission condition in the loop, and adjusting the transmission. equivalent of the loop until the abnormal condition no longer exists.

In a founwire circuit comprising a pair of transmission lines for transmitting in opposite directions and provided with means whereby said lines may be intercom nected i'ahrough terminal connections to terminal lines or connected together independ ently of said terminal connections, the method or" adjusting the transmission efficiency ot the four-wire circuit, which consists in producing a transmission path over a loop, including the two lines of the fourwire circuit interconnected independently of the teun'iinal connections, reducing the trans mission loss in the path thus produced so that singing takes place, and gradually increasing. the loss until singing just ceases.

6. In a tourovire circuit consisting of a pair of transmission lines for transmit-ting in opposite directions, each including amplittfyingmeans, said four-wire circuit be ing provided with means whereby said lines may be interconnected through terminal con nections to terminal lines or connected independently of said terminal connections with transmission devices having a total transmission equivalent double and opposite in sign to that to which it is desired to adjust each side of the four-wire circuit, the

method of adjusting the transmission edio ciency of the founwire circuit, which consists ID producing a transmission path over a loop which conslsts of the two lines of the four-wire circuit with their ends connected independently of the terminal connections and through said transmission devices, increasing the amplification of said amplify ing means until singing takes place over the loop thus produced, and gradually reducing the amplification until singing just ceases.

in four-wire circuit comprising a pair of transmission tines for transmitting in opposits directions and provided with means whereby the lines may be interconnected through terminal connections with terminal lines or interconnected independently of said. terminal connections with a transmisnon de vice having a total transmission equivalent opposite in sign and twice that to which it is desired to adjust the four-Wire circuit, the method of adjusting the transmission ciliciency of the four-wire circuit, which consists in producing a transmission path over" a loop includng the two lines of the tourwire circuit with their ends connected together through said transmission device independently of the terminal connections, re. ducing the loss in the path thus produced so that singing takes place, and gradually increasing the loss until singing just ceases.

8. In a four-wire circuit comprising a pair of transmission lines for transmitting in opposite directions and each including amplifying means, said circuit being provided with means whereby the lines may be intercom nected through terminal connections to ter niinal lines or'connected independently of said terminal connections the method oi adjusting the transmission etliciency of the four-Wire circuit, which consists in producing a transmission path over a loop inciud" ing said pair of lines with their ends inter" connected independently of the terminai connections, increasing the amplification of said amplifying means until singing takes place over the path thus produced, and gradually decreasing the amplification until singing just ceases.

9. In a signaling system, a two Way repeater circuit, means for connecting! the two sides of the circuit together to form a closed path in which singing will take place when the amplification in the path exceeds the loss, means to adjust the circuit, and means controlled by the singing of the circuit to brim the adjustment to an end when the amplification in the path is substantially equal to the loss.

10. In a signaling system, a four-Wire transmission circuit including a pair of transmission lines for transmitting in opposits directions, means to interconnect the ends of said lines independently oi terminal connections, and means to reduce the loss of said lines so that singing takes place over the circuit thus formed and to gradually increase the loss until singing just ceases.

11. in a, signaling system, a four-Wire transmission circuit including a pair of transmission lines for transmitting in oppo site directions, means to interconnect the ends of said lines, means to reduce the loss of said lines so that singing takes place over the circuit thus formed, and means responsive to the singing thereby produced to gradually increase the loss of. said lines until singing just ceases.

[12. in a signaling system, a four-wire transmission circuit including a pair of transmission lines for transmittingin oppo site directions,,ainplitying means in said lines, means to interconnect the ends of said lines independently of terminal connections, and means to increase the amplification of said amplifying means so that singing takes place over the circuit thus formed end to gradually decrease the amplification until singing just ceases.

13. in a signaling system, a four Wire transmission circuit including a pair of transmission lines for transmitting in opposite directions, amplifying means for said lines, means to interconnect the ends of said lines, means to increase the amplification of said amplifying means so that singing takes place over the circuit thus formed, and means responsive to the singing thereby pro-' duced to gradually decrease the amplification until singing just ceases.

14. In a signaling system, a four-Wire transmission circuit including a pair of transmission lines for transmitting in opposite directions, means to interconnect the ends of said lines through a transmission dc- I vice having a transmission equivalent opposite in sign and double that to which it is desired to adjust each side of the four-Wire circuit, means to reduce the loss of said lines so that singing takes niece over the circuit thus formed, and means responsive to the singing thereb produced to gradually iniercase thecloss 0 said lines until singing just ceases.

"5. in a signaling system, a four-wire" trhnsmission circuit including a pair of transmission lines for transmitting in opposite directions, amplifying means for said lines, means to interconnect the ends of said lines through a transmission device having a transmission equivalent double and opposite in sign to that to which it is desired to adjust each side of the four-Wire circuit, means to increase the amplification of said amplifying means so that singingtakes place over the circuit thus formed, and means responsivc to the singing thereby produced to gradually decrease the amplification until singing just ceases '16. in a signaling syste a four-Wire transmission circuit includi g a pair of transmission lines for transmitting in opposite directions, terminating two-Wire lines to which the ends of said pair "of transmission lines may be connected, means to disconnect said pair of transmission lines from the terminating two-Wire lines and inter connect the ends thereof through a trans mission device having a transmission equiva lent double and opposite in sign to that to which it'is desired to adjust each side at the four-Wire circuit, means to reduce the loss in the four-wire circuit so that singing wil the ends bit said pair of irsnsinission lines syssem, a four-wire may he connected; mesns to disconnect saicl pair of transmission lines from the tern'iineting iLWO-Wlffi lines and interconnect the ends teereoithrough :1 transmission device having a transmission equivalent double and opposite in sign to that to which it is desired to niljust each side of the ionic-Wire circuit means to increase the amplification of said amplif' ing means so that singing takes place over the circuit thus formed. and means responsive to the singing thereby PETOClllQEd to gradually decrease the m plificstionhintil singing just ceases.

ill. in a signaling system, a four-Wire ticnsmissio circuit includin a pair of transmission lines for transmitting in opposite dicections, amplifying means for said "ensmission lines, on automatic switch normal position. and being adapted, silvsncecl thereiirom or released and t1 means uncler the control of. said switch for determining the amplification of said amplifying means, means to interconnect the ends of said transmission lines and to release said switch, means responsive to the release oi'saicl switch for increasing the amplification of the amplifyling means so that singing: takes place over the circuit formed by the interconnected psir of transmission lines, and means responsive to the singing thereby produced for advancing said switch until singing justceases.

19. .ln s signalling system 2i pair of transmission circuits, each transmission circuit including amplifiers, and means for simul' taneously adjusting the gain of the simplifiers in the two circuits While maintaining the normal plate potentials and filament currents of said amplifiers constant.

20. ln s signalling system a pair of transmission circuits, amplifiers in each of said transmission circuits, and means for simultaneously adjusting the gain of the amplifiers in both circuits in the same iiirection while maintaining the normal plate poten tials and. filament currents of said smpli-= fiei's constant.

In testimony whereof, I have signed my name to this specification this sixth day of September 1918. ALV l3. ULARK. 

